There are 2 vehicles to collect Cisco IOS-based switch logs (can’t talk about CatOS - have none of those). One is via syslog and the other is via snmp. The latter will require the snmp plug-in for Graylog to be installed. I have found that syslog provides pretty useless data while snmp is superior in terms of answering the questions you want answered such as “what mac addresses are associated with particular switchports, etc”
In summary for snmp one needs a plug-in and of course configuring the traps that you want to be triggered on the cisco side